Dysregulated inflammation is important in the initiation and progression of atherosclerosis. In studies supported by this grant for the past 15 years, our laboratory has cloned one of the key inflammatory response genes, cyclooxygenase (COX)-2 and studied its role in the vascular system. Studies supported by this grant have also shown that the RNA binding protein HuR regulates the COX-2 gene at the post-transcriptional level. Given that HuR is a regulator of many inflammatory response genes, and its in vivo function is poorly understood, we developed Hur knockout mice and have begun to investigate its role in vivo. In this competitive renewal, we will focus on post- transcriptional regulation of vascular inflammation by the RNA regulator HuR. Thus the central hypothesis is that HuR-mediated post-transcriptional gene regulatory mechanisms in differentiated myeloid and endothelial cells restrains exaggerated inflammation and maintains normal vascular homeostasis. Aberrant regulation of HuR-mediated post-transcriptional mechanisms results in the cellular phenotypic change and accelerates the progression of atherosclerotic vascular disease. Therefore, we are proposing the following three specific aims. In the first specific aim, we will examine the hypothesis that HuR function in differentiated myeloid compartment controls monocyte/macrophage inflammatory phenotype. Second, we will examine the role of HuR-regulated post-transcriptional regulation on basal laminar shear stress induced and cytokine-induced inflammatory states of vascular endothelial cells. Third, we will examine the hypothesis that HuR- mediated post-transcriptional gene regulatory mechanisms restrains vascular inflammation and that absence of such mechanisms result in accelerated atherosclerosis in mouse models. We anticipate that these efforts will lead to new insights into our understanding of atherosclerosis that may ultimately lead to novel therapeutic approaches.